1. The Field of the Invention
The present invention relates to single-pot synthesis of texturized metal oxide catalysts, activation of these catalysts to metals, metal oxides, or metal carbides, and properties of these catalysts.
2. The Relevant Technology
While the synthesis, characterization, and exploitation of nanometer-sized catalytic materials has been practiced for many decades, the science and technology have in just the last 10-15 years greatly expanded in depth and breadth. The expanded exploration of new properties and uses for nanoscale metals and metal oxides is underway in a variety of disciplines, including chemistry, physics, material science, and engineering. Many new applications of nanoparticle technologies have been or will be soon commercialized, including new methods for synthesis of nanoparticle catalysts. Much of present-day catalyst technologies are relatively mature having been manufactured commercially on a large scale for over 100 years using increasingly more detailed, multistep, labor-intensive methods that enable sophisticated, multilayer catalysts to be made and ensure quality control. While this multi-step, labor-intensive approach is probably justified for production of highly sophisticated catalyst products, such as multilayer, wash-coated monolithic catalysts used in auto emissions control, there is a clear need for a more economical and efficient art, i.e., simple 1 or 2-step methods for producing multi-component catalysts containing nanoparticles of uniform size and high-purity. Such catalysts might include supported or texturally promoted metal, mixed-metal (alloy), metal oxide, and mixed-metal oxide nanoparticles with improved properties and performance in diverse applicants.
The prior art for preparation of supported metal oxide, metal carbide, and metal catalysts typically involves deposition of the active component onto a catalyst support (also known as a textural promoter) by impregnation, adsorption, ion-exchange, or precipitation followed by washing, drying, heating (e.g., calcination), and activation, e.g., reduction in H2 to form supported metals and in a H2, CO mixture to form a carbide. Unsupported, texturally promoted oxide, metal, or carbide catalysts are typically prepared by precipitation of a complex high surface hydroxide, oxide or carbonate containing the active component followed by washing, drying, separate addition by impregnation of the precursor of textural promoter (textural stabilizer or texturizing agent), a second drying, calcination and activation. Catalyst systems with about 10-30% textural promoter are said to be “unsupported” and catalyst systems with more than 50% of a textural promoter are referred to as “supported”. The term “textural promoter” or “texturized” is used herein to include materials such as, but not limited to, binders, stabilizers, carriers and supports. It should be mentioned that in the prior art the support or textural promoter is sometimes coprecipitated from its precursor salt with the active material. More typically, a highly porous ceramic textural promoter such as alumina, titania, silica, zirconia, or ceria, is first prepared by precipitation of the metal oxide precursor salt, calcined and formed into a structured material, e.g., spray-dried to form spheres, extruded into pellets or dip coated on to various matrix structures. The desired catalyst is then typically formed separately in a second step on the previously prepared support by impregnation, precipitation, or by chemical vapor deposition of volatile precursors of the catalytic phase inside the support pores, followed by calcination and activation of the catalytic materials by reduction, carbiding, or sulfiding. Details and principles of the prior art of catalyst preparation are found in books by Stiles and Koch [1995]; Bartholomew and Farrauto [2006], and Regalbuto [2007].
Examples of various supports and procedures for making supports are disclosed in U.S. Pat. Nos. 2,749,216; 2,796,326; 2,917,366; 3,019,080; 3,038,784; 3,042,696; 3,244,972; 3,419,352; 3,823,895; 3,898,322; 3,941,719; 3,944,658; 3,987,155; 4,154,812; 4,172,809; 4,175,118; 4,275,052; 4,387,085; 4,532,072; 4,579,729; 4,676,928; 5,455,019; 5,480,630; 5,593,654; 5,622,684; 5,863,515; 6,001,326; 6,027,706; 6,129,904; 6,555,496; 6,761,866; 6,764,672; 7,090,824; 7,163,963; 7,235,224; 7,341,976; 7,442,290; 7,534,415; and 7,807,605.